Many compositions used for skin treatment contain emollients or humectants in lotion, cream or gel form. Such product are applied by evenly spreading the product on the skin. Upon loss of water, the product dries providing humectants and emollients to the epidermis.
Water soluble gels that form protective films of various types are known. For example, U.S. Pat. No 4,393,048 discloses a water soluble hydrogel of alkali metal alginate and glycerine that dries to a non-toxic, pliable protective film. U.S. Pat. No. 3,949,742 discloses a transparent medical dressing which performs as a synthetic film over skin wounds. Water soluble polyesters, for example U.S. Pat. No. 4,502,976, are used to form cross-linked bioerodible hydrogels. The hydrogels, suitable for carrying water soluble therapeutic macromolecules and for implantation in living mammals, are produced by a complex polymerization process without using water soluble metallic ions.
U.S. Pat. No. 3,879,168 to Franklin discloses a surgical dressing made of partially soluble alginic materials in the form of gauze or wool characterized by a pH of 4 to 7 and a calcium content of 2-6% by weight comprised of a laminate of a thin layer of non-porous segmented polyurethane sewn to foam.
U.S. Pat. Nos. 3,734,874, 4,233,196, 4,335,220, 4,304,900, 4,304,901, and 4,300,580 describe water-dissipatable, metalable polyesters that are useful as adhesives, coating materials, films, packaging materials and other products that can be dissolved, dispersed or otherwise dissipated in water or aqueous solutions. These polyesters, however, are not cross-linked using metallic ions and cast into shapes to entrap water, humectants and/or emollients within the hardened cast.
As explained in a technical publication from Eastman, the water dispersability of the AQ polymer is largely attributed to the presence of ionic substituents attached to the polymer chain. A simplified representation of the polymer is shown below: ##STR1## wherein "A" is an aromatic dicarboxylic acid moiety some of which have sodiofulfo (--SO.sub.3.sup.-, Na.sup.+) substituents, "G" is an aliphatic or cycloaliphatic glycol residue and "OH" is a hydroxy end group.
It is the sodio sulfo group which impart the water dispersability to the polymer. To cross-link with multivalent metallic ions and obtain the moldable shapes of this invention, the multivalent metals salts must be added and mixed according to the teaching of this invention. Departing from this process results in non-compatible mixtures of non-commerical properties. Eastman technical publications teach the synthesis and preferred methods for crosslinking water dispersible polyesters and polyesteramides with other resins through high temperature curing process and subsequent drying of the cured resins, but specifically warn against the use of the heavy metal salts included in this invention as being not compatible with the polymers used in this invention.